Microfabricated surfaces for the physical capture of insects

ABSTRACT

Novel devices and methods of capturing, controlling and preventing infestation of insects using microfabricated surfaces are provided. In particular, a mechanism of insect capture inspired by the microstructures of the leaf surfaces of plants and the key features of those surfaces with respect to the capture and control of pests have been determined and engineered into a variety of microfabricated surfaces capable of reproducing the effectiveness of these physical capture methods.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 14/381,890,filed Aug. 28, 2014, which application is a national stage applicationof Application No. PCT/US2013/027772, filed Feb. 26, 2013, whichapplication claims priority to Application No. 61/604,808, filed Feb.29, 2012, the disclosures of which are incorporated herein by referencein their entirety.

STATEMENT OF FEDERAL FUNDING

The invention described herein was made in the performance of work underNSF Grant No. CHE-1057638, and the federal government may have rights init subject thereto.

FIELD OF THE INVENTION

The current invention is generally directed to methods of capturing,controlling and preventing infestation by insects; and more particularlyto microfabricated surfaces for such use.

BACKGROUND OF THE INVENTION

Bed bugs (Cimex lectularius L.) are an ancient scourge that have made adramatic comeback in recent years across the globe, infesting structuressuch as homes, hotels, schools, movie theaters, and hospitals. (See,e.g., Saenz V L, et al., J. Med. Entomol. 49, 865-875; Harlan J H.,Outl. Pest Manag. 18, 57-61 (2007); and Potter M F, et al., Pest WorldSeptember/October, 8-20 (2010), the disclosure of which is incorporatedherein by reference.) There was a decline of bed bug infestations in the1940's and 1950's following the application of DDT and other potentpesticides legal at the time. The recent resurgence of bed buginfestations occurring both domestically and internationally has led toa renewed interest in the development of new, more environmentallyfriendly and sustainable methods to capture, control, and prevent bedbugs.

To date, the primary strategy for bed bug abatement has been to developand apply chemical pesticides. However, bed bugs have grown resistant tomany of the commonly used pesticides making this approach increasinglyineffective. In addition, reliance upon pesticides is increasinglyperceived as imprudent because of the large amount of potentiallyharmful chemicals that must be applied indoors in bedrooms and othersensitive locations. Non-chemical abatement methods such as heat, cold,vacuuming, and bed encasement, are being utilized as well but tend to belaborious, costly, and frequently ineffective. Such methods also tend tobe curative rather than preventative in nature.

For many years, bean leaves have been known to capture bed bugs.Historical reports describe the capture of bed bugs in Balkan countriesby leaves from bean plants strewn on the floor next to beds. (See, e.g.,Potter M F, Amer. Entomol. 57, 14-25 (2011), the disclosure of which isincorporated herein by reference.) During the night, bed bugs walking onthe floor would accumulate on these bean leaves, which were collectedand burned the following morning to exterminate the bed bugs. Thecapture of bed bugs by the bean leaves was attributed to the action ofmicroscopic plant hairs (trichomes) on the leaf surfaces that wouldentangle the legs of the bed bugs. (See, for example, Richardson, H. H.,J. Econ. Entomol. 36, 543 (1943), the disclosure of which isincorporated herein by reference.) The disadvantages of this approachinclude: the supply of a sufficient number of fresh bean leaves, theinconvenience of having leaves spread on the floor, the inconsistenciesinherent in such naturally occurring materials, and the rapidwilting/desiccation of the leaves that stop them from functioning in bedbug capture for longer than overnight. In addition, because the beanleaves are limited as to how and where they may be applied, bed bugs areable to avoid capture by crawling along surfaces that cannot easily becovered by the leaves.

Despite its limitations, this physical capture mechanism is a source ofinspiration in the development of new and sustainable non-chemicalmethods to control the burgeoning numbers of bed bugs. A purely physicalmanagement method has the additional advantage that it would avoid theproblem of pesticide resistance that has been documented extensively forthis insect. (Romero A, et al., J. Med. Entomol. 44, 175-178 (2007);Yoon K S, et al., J. Med. Entomol. 45, 1092-1101 (2008); Zhu F, et al.,Arch. Insect Biochem. 73, 245-257 (2010); and Mamidala P, et al., BMCGenomics 13 (2012), the disclosure of which is incorporated herein byreference.) Accordingly, a need exists to create improved techniques anddevices to capture, control and prevent infestation by bed bugs andother insects.

SUMMARY OF THE INVENTION

In some embodiments, the invention is directed to a microfabricatedinsect capturing surface including:

-   -   a substrate defining a plane;    -   a plurality of insect capture surface microstructures each        formed from a flexible elongated member, the plurality of        surface microstructures being disposed on the substrate with a        variable orientation to the plane of the substrate and at a        density sufficient such that multiple insect capture surface        microstructures are capable of simultaneously interacting with        an insect disposed thereon;    -   wherein at least some of the surface microstructures have a        recurved body capable of entangling the insect, and wherein at        least some of the surface microstructures include a piercing        element being sufficiently rigid and sharp to pierce the insect        body; and    -   wherein the surface microstructures are formed from a material        having a breaking stress sufficiently large to avoid breakage        during interaction with the insect.

In some such embodiments, each of the plurality of insect capturesurface microstructures has a recurved body, and wherein at least onepiercing tip is incorporated onto each of said insect capture surfacemicrostructures.

In other such embodiments, the piercing tip is disposed at theterminating end of the elongated member. In these embodiments, thesurface microstructures may include at least two piercing tips, andwherein the piercing tips are disposed along the body of elongatedmember.

In still other embodiments, the recurved body is formed in a shapeselected from the group consisting of a hook, curve, loop or hoop.

In yet other embodiments, the piercing tip is selected from the groupconsisting of a sharp point, hook or barb.

In still yet other embodiments, the plurality of surface microstructuresare dimensioned such that engage the underside of the insect body.

In still yet other embodiments, the piercing tip has a diameter of about100 to 1000 nm.

In still yet other embodiments, the elongated member has a Young'sModulus of from 1 to 23 GPa.

In still yet other embodiments, the surface microstructures are modeledon a plant trichome. In these embodiments, the plant trichome may bemodeled on one plant selected from the group Phaseolus coccineus,Phaseolus vulgaris, Phaseolus limensis, Passiflora morifolia,Cynnoglossum offtcinale and Caiophora coronaria.

In still yet other embodiments, the surface microstructures are disposedon the substrate in a density of between 20 to 300 surfacemicrostructures per millimeter.

In still yet other embodiments, the surface microstructures are formedfrom a material selected from the group consisting of polymericmaterials, natural fibers, metals, oxides and nano- or micro-engineeredstructures.

In still yet other embodiments, the elongated member is formed of ahollow body.

In other embodiments the invention is directed to a method ofmanufacturing a microfabricated insect capturing surface comprising:

-   -   providing a substrate;    -   disposing a plurality of insect capture surface microstructures        thereon, each formed from a flexible elongated member, the        plurality of surface microstructures being disposed on the        substrate with a variable orientation to the plane of the        substrate and at a density sufficient such that multiple insect        capture surface microstructures are capable of simultaneously        interacting with an insect disposed thereon;    -   wherein at least some of the surface microstructures have a        recurved body capable of entangling the insect, and wherein at        least some of the surface microstructures include a piercing        element being sufficiently rigid and sharp to pierce the insect        body; and    -   wherein the surface microstructures are formed from a material        having a breaking stress sufficiently large to avoid breakage        during interaction with the insect.

In some embodiments, the process of depositing is conducted by one ofeither a double molding or etching process.

In other embodiments, the method further comprises coating on orincorporating within the surface microstructures an additive materialselected from the group consisting of oxide particles and a metallicmaterial. In these embodiments, the additive material may be depositedby a technique selected from one of either physical vapor deposition orelectro deposition.

In still other embodiments, the process of depositing is conducted by amicroneedle technology.

In yet other embodiments, the recurve is formed into the surfacemicrostructures by one of either an oblique e-beam irradiation or metaldeposition.

BRIEF DESCRIPTION OF THE DRAWINGS

The description will be more fully understood with reference to thefollowing figures and data graphs, which are presented as exemplaryembodiments of the invention and should not be construed as a completerecitation of the scope of the invention, wherein:

FIGS. 1A to 1D provide: images of a scarlet runner bean leaf in visiblelight (A), and viewed in SEM (B, C, D) showing the sharp points on thehooked trichomes, and their variable spacing and orientation on thesurface of the leaf.

FIGS. 2A to 2E provide: (A) a schematic of embodiments of an insectcapture surface, (B) a schematic of embodiments of an insect capturemicrostructure, (C) schematics of alternative embodiments of insectcapture microstructures, (D) a top view of an insect capture surface andthe density of microstructures on a surface, and (E) a schematic of anembodiment of an insect capture surface showing the variableorientations of disposed surface microstructures.

FIGS. 3A to 3E provide: schematics of (A) fabrication of biomimeticsurfaces from bean leaves (1-3), a negative molding material is pouredonto a leaf surface and pressure is applied (4-6), the leaf is removed,and the negative mold is filled with the positive replica material (7),and the negative mold is removed leaving the biomimetic replica; (B & C)LV-SEM images of the bean leaf show the surface density of trichomes andthe recurved, sharp trichome tips; and (D & E) SEM images of thereplicate materials appear identical to the natural leaves.

FIGS. 4A & 4B provide SEM images of a cross-section of negative moldingmaterial showing an embedded natural trichome tip that has broken offthe natural leaf trichome during molding.

FIGS. 5A to 5D provide: LV-SEM images of bed bug legs on bean leafsurfaces with hooked trichomes, where (A) shows piercing under apretarsal claw leads to capture of a bug by a leaf, (B) piercingoccasionally occurs at a tarsal intersegmental membrane, also causingcapture of a bug, (C) a higher magnification of piercing from (A), and(D) in contrast, hooking causes momentary snags of a bug leg.

FIG. 6 provides an image of the underside of a bed bug tarsus showing adangling broken trichome as evidence of piercing.

FIGS. 7A to 7D provide images showing the discrimination between naturaland synthetic trichome tips on hybrid surfaces using energy dispersivespectroscopy (EDS), where (A) is an LV-SEM image of a trichome on anatural bean leaf surface and the locations of EDS spectra areidentified ((a1) shows a strong silicon signature compared to the base(a2) and leaf surface (a3)); (B) shows an SEM image showing both ahybrid tip (b1) and non-hybrid tip (b2) and their corresponding EDSspectra showing the presence or absence of detectable siliconrespectively; (C) shows EDS mapping of trichomes on the leaf surfaceshowing the presence of silicon on the natural trichomes; and (D) showsa representative synthetic surface showing examples of natural trichometips incorporated into the polymer surface (indicated by the presence ofsilicon) along with an example of a fully-synthetic trichome (indicatedby the circle).

FIGS. 8A to 8C provide: (A) diagrams, and (B & C) SEM imagesdemonstrating the successful molding of the hooked trichomes ofPhaseolus vulgaris (Kidney bean) in polyvinylsiloxane (the negativemold).

FIGS. 9A to 9C provide images of typical biomimetic hooks fabricated bydual molding method, wherein: (A) shows low magnification image showingepoxy recurved trichomes from a scarlet runner bean, (B) a vein on abiomimetic kidney bean leaf where the hooks are made from wood glue, and(C) a close view of the sharp, epoxy hooks replicated from a scarletrunner bean.

DETAILED DESCRIPTION OF THE INVENTION

This description embodies constructs and methods of capturing,controlling and preventing infestation of insects using microfabricatedsurfaces. In particular, the mechanisms of bed bug capture by themicrostructures of the leaf surfaces of four species of plants:Phaseolus vulgaris (three varieties used: kidney bean, pole bean, andgreen bean), Phaseolus coccineus (scarlet runner bean), Phaseoluslimensis (lima bean) and Passiflora morifolia (passion flower), havebeen examined and the key features of those surfaces with respect to thecapture and control of pests determined and engineered into a variety ofmicrofabricated surfaces capable of reproducing the effectiveness ofthese physical capture methods.

Although hooked trichomes have been documented in insect capture attimes in the literature: the capture of nymphal and adult leafhoppers byPhaseolus vulgaris (Pillemer, E.; Tingey, W., Science 1976, 193,482-484, the disclosure of which is incorporated herein by reference), avariety of insects in the Arizona desert by Mentzelia pumila (Eisner,T.; Eisner, M.; Hoebeke, E. R., Proceedings of the National Academy ofSciences 1998, 95 (8), 4410-4414, the disclosure of which isincorporated herein by reference), and the capture of caterpillars byPassiflora adenopoda (Gilbert, L. E., Science 1971, 172, 585-586, thedisclosure of which is incorporated herein by reference), to date theonly report of hooked trichomes on a plant capable of capturing bed bugsis the bean plant, Phaseolus vulgaris. (Richardson, cited above.)Effective capture of bed bugs by hooked trichomes on other surfaces havenow been examined, and those features that tend to lead to capture ofsuch insects determined. In particular, it has been discovered that thespecific material properties and shape of microstructures, the density(spacing) of trichomes on the surfaces of specific types of plants, andtheir orientation is extremely variable (as shown in FIG. 1), andappears to be directly related to efficiency of bed bug capture acrossplant species. In addition, specific densities of trichomes have alsobeen shown to affect the capture of other insects, such as, for example,leafhoppers.

All of the plant species studied appear in the first instance to have asimilar surface texture that contains flexible microscopicmicrostructures or hairs having pointed or barbed ends, that are oftenhooked, i.e., a trichome structure. In order to understand the captureeffectiveness of these natural surfaces, the features that make suchsurfaces effective have been evaluated. (These studies are described ingreater detail in the Exemplary Embodiment section below.) For example,optical and SEM images of leaf undersurfaces are shown in FIG. 1. Inaddition, bed bugs were placed individually onto leaves and theirmovements recorded as digital movies. As a bed bug walks on one of theseleaves, entanglement of a leg by a trichome causes a visible change inits walking behavior. Based on these observations, two discreetcategories of entanglement have been identified:

-   -   a momentary snag of a leg with the insect still able to break        away (usually within a second); and    -   a more involved and irreversible snare in which a visibly        struggling insect is unable to pull away.        The production of effective insect capture surfaces depends on        determining and maximizing the production of surface        microstructures that lead to the second, irreversible type of        entanglements.        Embodiments of Insect Capture Surfaces

Based on detailed observations of several varieties of natural leafsurfaces and their specific ability to capture insects, it is nowpossible to create effective insect capturing surfaces that maximizeirreversible snaring interactions with the insects of choice. Because ithas now been discovered that a simply hooking action is insufficient topermanently snare the insects, embodiments include surfacemicrostructures that are designed to both entangle and pierce. As shownin FIG. 2A, these surfaces (10) generally include a plurality ofentangling and piercing microfabricated insect capture microstructures(12) formed on a supporting substrate (14). To optimize the probabilityof a piercing interaction between the insect capture microstructure andthe vulnerable portion of the insect, three separate factors need toengineered: the density of the capture microstructures, the orientationof the microstructures relative to the plane of the substrate, and thestructure of each of the individual capture microstructures. Embodimentsof each of these elements are described above.

Turning first to the structure of the individual microstructures, theobservations of the interactions of insects with different plantstructures have shown several important functional aspects of asuccessful piercing capture microstructure. Embodiments of exemplarystructures are shown in FIGS. 2B and 2C. As shown, the microstructuresgenerally comprise a flexible elongated member (16) that provides atleast an entangling function. The surface must also include a piercingmicrostructure disposed thereon (18). These microstructures may beindependent or, as shown in FIGS. 2A to 2C, they may be combined into asingle structure. However, regardless of how the capture microstructuresare individually engineered, the capture surface should have thefollowing functional characteristics: resiliency or flexibility, theability to entangle, and the ability to pierce an insect.

First, to ensure that the elongated member is capable of moving acrossthe body of the insect to entangle and interact with a vulnerableportion of the insect, and to make it more likely that the insect willbecome entangled, and make it more difficult for the insect to removeitself from the piercing member, the elongated member should be flexiblyresilient. The flexibility of the members may be a function of thematerial from which the member is made, it may be a function of thestructure of the member, or it may be a combination of these. Morespecifically, the flexibility of the member may be ensured by formingthe member with a curved or recurved portion (20). This curve/recurvedportion (20) provides a natural resilient spring functionality to theelongated member (16). In some instances, as shown in FIG. 2B, therecurved portion is positioned at the distal end of the elongated membersuch that the overall shape of the insect capture microstructure is of ahook or J-shaped structure. Alternatively, as shown in FIG. 2C theentire elongated member may form a curve, or may be curved to such anextent that the member forms a hoop or a loop. These structures may behollow or solid, but should be sufficiently flexible that they willdeform when interacting with an insect of interest.

Regardless of the nature of the curved/recurved portion of the elongatedmember (16), a piercing element (18) should be incorporated into theoverall functionality of the surface. The piercing member may compriseany member suitable for piercing an insect, including, for example, arigid straight or curved sharp tip, barb, or hook (18), which is eitherdisposed directly on the substrate or located on the elongated memberitself, either at the terminating end of the member or somewhere alongthe curved/recurved portion (20) of the member.

The dimensions of the elongated member and piercing structure, and theirplacement may be controlled to increase the probability that a piercingevent will incur when the microstructures interact with and pierce aninsect. More specifically, the sharpness of the natural trichome pointsare designed to be sufficiently rigid and sharp to ensure the ability topierce the target insect. In some embodiments, for example, the piercingmicrostructure may have a tip dimensioned from about 100-1000 nm, and insome embodiments about 100 to 300 nm. Likewise, as shown in FIG. 2C thesharp point, hook, or barb may be disposed at the terminal end of theelongated member, or along the body of the curved elongated memberitself, or on separate structures disposed along the elongated member.In the case of the separate structure it may take any suitable form, butin some embodiments comprises barbed hoops or partial loops. Regardlessof the positioning, shape, or nature of the piercing element, in theseembodiments the piercing element is formed to be sufficiently rigid andsharp that they are capable of piercing the vulnerable areas on aninsect or bed bug, such as the underside of the insect/bug body or legsor tarsus, or other vulnerable area of the body.

In embodiments where the piercing element is located along the elongatedflexible member, the member is also dimensioned such that the piercingportion of the member is capable of interacting with the vulnerableportion of the insect of interest. For example, on the bed bug one ofthe most vulnerable target portions is the underside of the insect, andmore particularly the areas on the tarsus underneath the tarsal clawsand the intersegmental membrane between the tarsal subsegments, which isapproximately 50 to 100 microns in height.

An exemplary structure would be one that mimics the shape andfunctionality of a plant trichome. However, it should be understood thatany structure having suitable length, strength and structuralmicrostructures may be used in association with the insect capturesurfaces described herein. Likewise, although embodiments of structuresformed from specific polymer materials are described in the sectionsbelow, it should be understood that the substrate and insect capturemicrostructures of the embodiments may be formed from any materialhaving suitable breaking stress properties including, polymericmaterials, natural fibers, metals and oxides. Alternatively, thestructures may be made of materials or composites that includemicroengineered structures such as carbon-nanotubes or other suchmaterials. Finally, the breaking stress of the material from which theinsect capture microstructures should be formed should match or exceedthe breaking stress of a natural plant trichome material, and morespecifically the kidney bean trichome. In a rare example of mechanicaltesting of trichomes, individual bending tests resulted in a range of1-23 GPa for Young's modulus (flexural) (fruit hooks of Galium aperine).(See, Gorb E V, et al., In Design and Nature: Comparing Design in Naturewith Science and Engineering (C A Brebbia, L Sucharov, P Pascolo, Eds.),pp. 151-160. Southampton, UK: WIT Press (2002), the disclosure of whichis incorporated herein by reference.) Therefore, in some embodiments thematerials used to generate the synthetic surfaces should be comparablein material properties to these trichome walls. Qualitatively, thesebend test values demonstrate that plant trichomes have a large breakingstrain, as indicated by their ability to bend completely over andelastically return to an upright orientation without breaking. Inaddition, the curved portions of the trichomes are typically able tostraighten and elastically return to their curved configuration whenpulled from the negative mold; freeze-fracture of the negative moldsshowed none of the damage or ripping that would be caused by anon-straightened hook pulling through the material. Therefore,qualitatively the synthetic insect capture microstructures preferablyshow similar mechanical behavior in this regard.

Although the structure of the insect capture microstructures themselvesis important, as discussed above it is also important that thesemicrostructures be deposited on the supporting substrate in a mannerthat will allow them to function to capture the insects of interest. Inparticular, in embodiments the orientation and density of themicrostructures on the substrate can be controlled to improve theperformance of the insect capture structures. In particular, in someembodiments the insect capture microstructures are disposed on thesubstrate with the following constraints:

-   -   The insect capture microstructures are disposed on the substrate        with a density sufficient that an insect will interact with        multiple microstructures simultaneously, and in fact preferably        (although not necessarily) that multiple legs of the insect will        be captured by the surface at once. Obviously, such a density        will be partially dependent on the insect being captured.        However in some embodiments, the density of capture        microstructures ranges from 30-200 microstructures/square        millimeter (as shown in FIG. 2D). Another way of describing the        distribution of elements in space is the linear distance between        the elements. Under this rubric, in some embodiments the range        of the “nearest neighbor” (linear distance from microstructure        to microstructure on the surface) ranges from 20-120        micrometers. These microstructures may be arranged randomly (in        the two-dimensional space of a leaf surface), or regularly (as        in a square or hexagonal grid), or a combination so long as the        density of microstructures is adequate.    -   Because it is desired that the microstructures interact with the        insect regardless of the orientation of the insect with the        substrate, it is preferred that the microstructures are placed        on the surface with variable orientation (i.e., the angle of the        longitudinal axis of the elongated member (22) to the horizontal        plane of the substrate, as shown in FIG. 2E) so that the        microstructures will interact with the insect from a variety of        angles and orientations.        It should be understood that though specific densities and        orientations are described herein that other densities and        orientations may be implemented for the specific insect or        capture structure used.

Turning to the construction of the substrate, although all of the aboveembodiments have shown a flat substrate of regular contour, it should beunderstood that the substrate may take any form suitable for theacceptance of the insect capture microstructures. For example, thesubstrate may be contoured or curved to conform to any desired surface.Likewise, the plane of the substrate may be undulating or include stepsor any other features desired for the specific application, or toenhance the likelihood of entangling the insect. Finally, the substrateitself may be made of any material compatible with the deposition of theinsect capture microstructures.

Embodiments of Methods of Forming Insect Capture Surfaces

The invention is further directed to a method for generating such insectcapture surfaces. The challenge in the microfabrication of such pestcapturing microfabricated surfaces is to accurately reproduce the highaspect ratio microstructures (e.g., sharp-tipped recurved trichomeswhich are about 50 microns long with a 10 micron diameter) present inthe plant surface morphology. Additionally, it is necessary tofaithfully reproduce the surface density and geometric orientation ofthe surface microstructures. Although a number of methods may be used,including three-dimensional growth, etching, deposition, etc., in oneembodiment the surfaces are formed with sufficient accuracy using amethod based upon a double molding process. (See, e.g., Schulte, A. J.,et al., Acta Biomaterialia 2009, 5, 1848-1854; and Koch, K, et al.,Bioinspiration and Biomimetics 2008, 3, 046002, the disclosures of whichare incorporated herein by reference.)

A schematic diagram of embodiments of the microfabrication processaccording to some embodiments of the invention, and consisting of theseven steps shown in FIG. 3. As shown in Steps 1-3, a desired surface(such as a bean leaf) is impressed into a flexible polymer (PresidentPlus Jet Light Body, a polyvinylsiloxane) thin film in order to create aflexible negative polymer mold (see FIG. 3). In Steps 4-6, the desiredsurface is removed from this mold and a positive replica is created inthe mold using an epoxy-based polymer. Finally, in Step 7, the negativemold is physically peeled off the epoxy thin film to create the activebiomimetic insect capture surface.

Although the molding method, using leaves with hooked trichomes asmodels, has generated extremely promising biomimetic materials for bedbug capture, it should be understood that additional options andmodifications may be made to further improve these materials. First,while a molding procedure was used to generate the synthetic surfaces itgenerates a solid (filled) object, which is necessarily less stiff inbending and twisting than a hollow object. The stalks of the naturaltrichomes are hollow, while the microfabricated trichomes generated viaa molding technique are solid (and therefore less flexible).Accordingly, it might be possible to increase the flexibility of themicrostructure by generating thinner (and therefore more flexible)microstructures using different techniques (a non-moldingmicrofabrication method).

Second, methods to manipulate the material properties post-molding maybe used, such as adding oxide particles to strengthen the material,and/or adding a metallic coating either by physical vapor deposition orelectro deposition. (See, Wetzel, B.; Haupert, F.; Zhang, M. Q.,Composites science and technology 2003, 63, 2055-2067, the disclosure ofwhich is incorporated herein by reference.) Also, other plant speciesoffer promising trichome geometries, including Cynnoglossum offtcinaleand Caiophora coronaria, both of which have barbed hooks on theirsurfaces. (Koch, K.; Bhushan, B.; Barthlott, W., Progress in MaterialsScience 2009, 54, 137-178, the disclosure of which is incorporatedherein by reference.)

In some embodiments, a micro-needle technology may be used, which wouldoffer the advantage of generating uniformly sharp structures of theproper length scale. (Henry, S.; McAllister, D. V.; Allen, M. G.;Prausnitz, M. R., Journal of Pharmaceutical Sciences 1998, 87 (8),922-925; and Park, J.-H.; Allen, M. G.; Prausnitz, M. R., Journal ofControlled Release 2005, 104, 55-61, the disclosures of which areincorporated herein by reference.) With pointed polymeric structures thenext challenge is to recurve the structures without dulling the sharppoints, which can be done with oblique e-beam irradiations or metaldeposition. (See, e.g., Kim, T.; Pang, C.; Suh, K Y., Langmuir 2009, 25(16), 8879-8882; and Choi, M. K.; Yoon, H.; Lee, K; Shin, K, Langmuir2011, 27, 2132-2137, the disclosures of which are incorporated herein byreference.)

Exemplary Embodiments

Studies were undertaken to identify the essential features of thecapture mechanics of bean leaves to guide the design andmicro-fabrication of biomimetic surfaces for bed bug capture. Theinteraction of bed bug tarsi with the microscopic plant trichomes wasevaluated by videography and scanning electron microscopy (SEM).Synthetic surfaces were microfabricated using a template method andevaluated for hindrance of bed bug locomotion. In order to validate thefidelity of the proposed replication process, a bean leaf was reproducedand both the negative and the positive molds were examined usingstandard high vacuum scanning electron microscopy (SEM) techniques.Finally, the ability of these microfabricated surfaces to interfere withbed bug locomotion has been evaluated by recording movies of live bedbugs running on these fabricated surfaces. In the study, bugs aredropped onto the hooked material and recorded for a minimum of oneminute, and it is shown that the bugs are hooked on the inventive microfabricated surfaces. The surfaces are scored by the number of steps abug takes until it appears to have trouble moving any tarsi (feet), inparallel with the studies of bug movements on the natural leaf surfaces.

Material and Methods

Experimental Organisms

Kidney beans (Phaseolus vulgaris L.) were raised from seeds (Johnny'sSeeds, Product 2554). Individual leaves (trifoliate, node≥1) weresevered where the base of petiole met the stem, were sealed in bags withmoistened paper to remain hydrated prior to experimentation, and wereused within a few hours. Bed bugs (Cimex lectularius) were raised at theUniversity of Kentucky and were not fed within three weeks before use.All bugs used were male adults.

Imaging Techniques

Digital movies were acquired on a Sony HDR-CX100 at 30 frames/s with aresolution of 2016 pixels by 1134 pixels (this corresponds to a spatialresolution of 0.1 mm for the field of view used). The camera waspositioned in a vertical orientation (viewing a bug on a surfacedorsally from above), while the leaf or synthetic surface was orientedhorizontally. A leaf or its synthetic analog was placed with the abaxialside (undersurface) facing upward, and a single bug was introduced tothe center of the surface by gently tipping the bug from a glass vialapproximately 2 cm above the surface. The abaxial side usually has agreater density of hooked trichomes than the adaxial side in manyspecies, including Phaseolus vulgaris [9-11, 18, 19] although this isnot universal [20, 21]. (Riddick E W, Wu Z., Biocontrol 56, 55-63(2010); Johnson B., B. Entomol. Res. 44, 779-788 (1953); Jeffree C E.,Insects and the Plant Surface (B Juniper, R Southwood, Eds.), pp. 23-64.London: Edward Arnold Ltd. (1983); Dahlin R M, et al., Econ. Bot. 46,299-304 (1992); Bauer G, et al., P. Roy. Soc. B-Biol. Sci. 278,2233-2239 (2011); Stenglein S A, et al., Aust. J. Bot. 52, 73-80 (2004);and Pillemer E & Tingey W., Science 193, 482-484 (1976), the disclosuresof which are incorporated herein by reference.) All recordings were madeat ambient temperature (22-24° C.).

All SEM imaging was performed on a FEI Quanta 3D FEG Dual Beam SEM (FEI,Hillsboro, Oreg.). For low-vacuum SEM (LV-SEM), captured bugs on leaveswere prepared by cutting the leaf around the captured bug to a sizeapproximating the size of an SEM stub, and mounting the leaf piece withits attached bug on the SEM stub with copper tape. In order to confirmand quantify the number of piercing trichomes, every specimen wasrepeatedly tilted to view underneath the tarsi of all six legs. LV-SEMimages were attained at a pressure of 0.6 mbar and 5 kV with water asthe ionizing gas. Bugs were still alive and resumed struggling afterremoval from the LV-SEM.

For high vacuum SEM (HV-SEM) imaging of replica materials, samples weresputtered with iridium (IBS/e, South Bay Technology, Inc) with a60-degree tilt angle and constant rotation for 4 minutes (˜5 nm Ir).Images of the microstructures were acquired at 5 kV.

EDS (50 mm X-MAX, Oxford Instruments, INCA 4.15) was performed using theFEI Quanta 3D FEG Dual Beam SEM (FEI, Hillsboro, Oreg.) on samples at 10kV with a current of 0.75 nA at a working distance of 8 mm. Elementalmapping was executed over the desired area for 230 s to determine thepresence of silicon. Carbon, oxygen, sulfur, and iron were also imagedas controls to account for the topography of the sample surface.Synthetic surfaces were prepared as described above for HV-SEM imagingincluding sputtering with iridium. Natural leaf controls used the sameEDS parameters, but in LV-mode at 0.6 mbar and without sputtering.

Techniques Used to Study the Locomotion Hindrance of Bugs by Surfaces

Digital movies were reviewed to identify changes in bug locomotionassociated with mechanical interactions with the natural leaf orsynthetic surfaces that interrupted normal movements. Incidents ofmomentary or prolonged struggling by the bug as one or more legs werestuck in place were tabulated. The number of locomotory cycles until abug experienced a momentary snag and until capture by a leaf werecounted. One locomotory cycle refers to a single step taken by each ofthe six legs. The number of steps was used rather than time because bugsvary in their walking speed and number of pauses on the surface likemost insects. Also, the number of locomotory cycles directly representsthe number of opportunities for leg/trichome encounters that can lead topiercing. Each bug was only used once.

Measurement of the Retention of Insects on Leaves after Initial Capture

In order to determine if a bug could move on a surface after its initialcapture, a time series of static images was attained for captured bugs(n=6). After capture by a leaf surface, an initial photo was immediatelytaken documenting the location of capture (using the same cameradescribed above). Subsequent photos were taken after 10, 20, and 30minutes. Images were imported into image analysis software (Canvas 12,ACD Systems International, USA), stacked, and oriented on top of oneanother, lining up the leaf outlines. A circle (4 mm diameter) wascentered over each bed bug for each of the four images and thecenter-to-center distance between these circles was calculated. It wasestimated that a displacement of approximately 6 mm of the circle centerwould result if a captured bed bug was able to rotate about a single legimpaled at its tip, and therefore a displacement of greater than 6 mmwould indicate that the bug was able to free itself during that timeinterval.

Measurement of Trichome Density

Trichome density (number of trichomes per area of leaf surface) wasmeasured on leaves with captured bugs, close to the points of capture.The lengths of these leaves ranged from 69-124 mm (base to tip, notincluding petiole); trichome density was not significantly related toleaf length (r2=0.36, n=10, slope of regression line is not significantat the P=0.05 level) and therefore leaf length was not included in otherstatistical analyses. LV-SEM images of the leaf surfaces were acquired,opened in ImageJ, and all trichomes on those images counted. An averageof 39 trichomes were counted over an average area of 0.44 mm² per leaf(n=11 leaves).

Microfabrication Techniques

Using kidney bean leaf surfaces as templates, biomimetic polymericsurfaces have been constructed for the capture of bed bugs (FIG. 3A).Some methods for generating biomimetic leaf surfaces are based upon adouble molding process that had been shown to reproduce complex leafarchitectures. (See, Koch K, et al., Bioinspir. Biomim. 3, 046002(2008); Schulte A J, et al., Acta Biomater. 5, 1848-1854 (2009); andKoch K, et al., Prog. Mater. Sci. 54, 137-178 (2009), the disclosure ofwhich is incorporated herein by reference.) First, a leaf was placed ina petri dish (100 cm² area) with its abaxial (undersurface) side facingupward. The negative polyvinylsiloxane molding material (President PlusJet Light Body, Affinis Light Body, or Affinis-Fast Light Body,Coltene-Whaledent, Inc.) was then poured onto the leaf surface and theother side of the petri dish was placed on top of the negative moldingmaterial with pressures ranging from 2 to 10 g/cm² duringpolymerization. The leaf was then peeled off of the negative mold. Thenegative mold was subsequently filled with a positive molding materialand left to dry overnight prior to removal. A variety of polymericpositive molding materials, various epoxies and glues with differenthardening rates and resin:hardener ratios were used in order to generateartificial trichomes with mechanical properties that span the largelyuncharacterized properties of natural trichomes (FIGS. 3B to 3E). Forexample, epoxies have Young's moduli (tensile) in the range 0.8-4.2 GPawere use, which compare well to plant cell walls (0.1-70 GPa). (See,e.g., Wetzel B, et al., Compos Sci Technol 63, 2055-2067 (2003); Zheng S& Ashcroft I A, J. Adhes. Adhes. 25, 67-76 (2005); Lilleheden L., Int.J. Adhes. Adhes. 14, 31-37 (1994); Burst N, et al., J. Adhesion 87,72-92 (2011); Katnam K B, et al., Int. J. Adhes. Adhes. 37, 3-10 (2012);Vincent J F V., J. Exp. Biol. 202, 3263-3268 (1999); Vincent J F V. 1990Structural Biomaterials Princeton, N.J.: Princeton University Press;Hiller S, et al., J. Texture Stud. 27, 559-587 (1996); Gibson L J, etal., 2010 Cellular Materials in Nature and Medicine Cambridge, UK:Cambridge University Press.; and Gibson L J, et al., J. R. Soc.Interface 9, 2749-2766 (2012), the disclosures of which are incorporatedherein by reference.) Some exemplary materials include: Loctite HeavyDuty Quick Set Epoxy (Henkel Corp.), Loctite Epoxy Extra Time (10:4ratio, 1:1 ratio) (Henkel Corp.), T88 epoxy (Systems Three Resins,Inc.), Titebond III Wood Glue (Franklin International), Bob SmithMid-Cure 15 min Epoxy (Bob Smith Industries, Inc), and Bob SmithSlow-Cure 30 min Epoxy (Bob Smith Industries, Inc).

Accurate replication of the sharp trichome tips is presumably crucial tofacilitate piercing of the bed bug cuticle by synthetic trichomes. Thesharpness of both natural and synthetic trichome tips was measured forseveral representative surfaces to the nearest half pixel (˜100 nm) inImageJ software using SEM images to evaluate whether the synthetictrichomes were sufficiently sharp.

Incorporation of Natural Trichome Tips into Hybrid MicrofabricatedSurfaces

In addition to generating completely synthetic surfaces, it was alsopossible to create hybrid synthetic surfaces with some percentage ofnatural trichome tips incorporated onto synthetic trichome stalks.Synthetic trichome tips can be indistinguishable from natural trichometips in SEM (FIGS. 3C & 3D) and therefore special analytical techniquesare required to unambiguously identify whether a tip is natural orsynthetic. Energy dispersive X-ray spectroscopy (EDS) was used toreliably identify natural trichome tips by looking for the chemicalsignature of silicon, which was present in large amounts in the naturaltrichome tips, but not in the synthetic polymers used. (See, Dahlin R M,et al., Econ. Bot. 46, 299-304 (1992); and Perry C C., Insects and thePlant Surface (B Juniper, R Southwood, Eds.), pp. 345-346. London:Edward Arnold Ltd. (1986), the disclosures of which are incorporatedherein by reference.) EDS mapping was used to estimate the percentage ofnatural tips on the microfabricated surfaces. Analysis of hybrids wasperformed by corroborating the elemental silicon maps with the electronimage in the INCA software. Four representative areas (each of typicalsize approximately 0.25 mm², e.g. FIG. 3E) per surface were analyzed andtheir trichome counts summed (an average of 93 trichomes were analyzedper surface). A trichome was deemed “hybrid” if there were more than 3pixels with silicon signal that matched with a trichome in the electronimage. The percent of hybrid trichomes was calculated from the number ofhybrid trichomes (from the Si images) divided by the total number oftrichomes (from the electron images). The percentage of natural tipsranged from 0-100% in the 38 microfabricated surfaces that werecharacterized by EDS mapping.

Any natural trichome tips incorporated into synthetic surfaces must havesnapped off the natural leaf, and therefore broken trichomes should bevisible on the natural leaf after being used to generate the negativemold. To verify this step in the molding process, LV-SEM was used toexamine the number of broken trichomes on a set of natural leaves aftermolding. This analysis also used four images acquired on each leaf atdifferent locations. The trichomes on each image were tallied todetermine the number of sharp, intact trichome tips and the number ofbroken tips on the natural leaf surface. The data acquired for the fourimages were summed and the percentage of broken trichomes was calculatedfor each leaf; results ranged from 0-95% broken tips per leaf.Statistical analyses confirmed that there was a significant correlationbetween the percentage of broken tips on a leaf surface and thepercentage of the number of hybrid trichomes on the fabricated surfacemade from that particular leaf (r2=0.50, n=30, P<0.0001, linearregression).

The presence of broken natural trichome tips in the negative molds afterleaf removal was confirmed using SEM (FIG. 4). The negativepolyvinylsiloxane molds were prepared for this analysis byfreeze-fracturing to generate a crack without surface deformations andmounted at a 90° angle with silver paint in order to observe theinterface. These samples were sputtered (˜5 nm Ir) and observed inHV-SEM at 5 kV. The images show that there are occasionally residualnatural tips in the negative mold.

Generating a Standard for Comparison with Natural Leaves

The number of locomotory cycles before a bed bug exhibited a snag whilerunning on a synthetic surface was compared to that measured on naturalleaves. However, a synthetic surface includes both synthetic and hybridtrichomes. If only hybrid trichomes (with natural trichome tips) arecapable of snagging or capturing bed bugs, the number of expectedlocomotory cycles to snag or capture can be estimated from theproportion of trichomes that are hybrid. A conservative approach wasused in the choice of a standard of 19 locomotory cycles (the 90thpercentile for the number of locomotory cycles that led to capture onnatural leaves, n=11 bugs). For each hybrid surface characterized by EDS(n=26 out of the 38 synthetic surfaces; 12 had zero hybrids), the numberof locomotory cycles on a hybrid surface that would be expected toresult in capture 90% of the time (number of locomotorycycles=19/(percentage of trichomes that were hybrid)) was clculated. Thenumber of locomotory cycles was counted for a bug running on a syntheticsurface until a momentary snag was observed (up to a maximum of 200cycles or the expected number based on the hybrid percentage, whicheverwas smaller). This made it possible to compare the performance of thedifferent surfaces in causing difficulties in locomotion.

Assessing Damage to Synthetic Surfaces

One possible reason that surfaces might not capture bed bugs could be ifthe hooks on the hybrid surfaces simply snapped off without impaling thebed bugs. In order to evaluate whether hooks snap off when walked on bybugs, three surfaces were examined in SEM both before and afterextensive exposure to bug contact during walking. These samples wereattached to SEM stubs, and examined under LV-SEM for hook number andintegrity on four different areas (each with a surface area of 2 mm²) oneach of the three surfaces. The total area of each of the three samplesof surfaces examined was approximately the same as the SEM stub: 130mm². The approximate surface contact area for all six tarsi of a singlemale adult bed bug is 0.15 mm². Therefore 870 locomotory cycles onaverage would be required for each part of a 130 mm² surface to bestepped on once (assuming each 0.15 mm² step is on a new area). In orderto conservatively ensure that each part of the surface would get steppedon at least once, 10 bugs were placed on each surface (sealed inside avial) and rotated slowly at 8 revolutions/minute (Barnstead ThermodyneLabquake Rotisserie Model C400110) to gently agitate the bugs so thatthey continued to walk over the surface for 18 hours; the total areaimpacted by 60 bug feet with 8 locomotory cycles/minute on average overan 18 hour period would be 10 times the area of the surface. After thesurfaces had been thoroughly walked on by bugs as described, the samelocations on these surfaces were re-evaluated in SEM. Comparison of thebefore and after images confirmed that no hooks had been broken and thatthe bed bugs were not damaging the synthetic surfaces.

Statistical Analyses

All analyses were performed using SAS statistical analysis software(Version 9.2; Cary, N.C.).

EXAMPLE 1 Mechanism of Bed Bug Capture by Bean Leaves

In order to evaluate the capture effectiveness of natural leaf surfaces,bed bugs were placed individually onto kidney bean leaves (Phaseolusvulgaris L.) and their movements recorded as digital movies. As a bedbug walked on a leaf, entanglement of any legs by trichomes caused avisible change in its walking behavior. It was possible to identify twodiscreet categories of entanglement: (1) a momentary snag of a leg withthe bug able to break away (usually within a second), and (2) a morelengthy and irreversible snag in which a visibly struggling bug isunable to pull away and is therefore considered “captured” by the leaf.It was usually impossible to see details of the trichome-bed buginteraction in situ using light microscopy because the trichomes arevery small (˜10 microns in diameter and 50-100 microns high) and wereoften underneath the tarsi. In order to visualize the actions of thetrichomes that corresponded to capture, live captured bed bugs wereexamined on leaves using LV-SEM after recording their capture. Every bugcaptured by a leaf had at least one piercing on one leg by a trichome(n=18 bugs). “Piercing” was defined as a clear and unambiguouspenetration of the insect cuticle by the trichome tip (FIGS. 5A to C);tilting the specimen was usually required for such confirmation becausepiercing generally occurred on the underside of the foot. The same legsthat appeared irreversibly snagged on the leaves in the movies of thestruggling bugs were confirmed as pierced in LV-SEM. Therefore, it waspossible to conclude that piercing is necessary for capture.Occasionally some legs were hooked by the trichomes (FIG. 5D), and weinferred that this hooking could lead to momentary snags.

Bed bugs were captured fairly quickly when walking on kidney beanleaves. Typically, a bug showed a visible momentary snag after only sixlocomotory cycles (one locomotory cycle refers to a single step taken byeach of the six legs) (median reported, range 0-13 cycles, “0” meansthat the bug displayed snagging behavior immediately on introduction tothe surface, n=11 bugs), and was captured after only nine cycles(median, range 0-39 cycles, n=11 bugs). This means that a bed bug wasusually captured within seconds after placement on a leaf. Bed bugscontinued to struggle after being pierced by a trichome, and thestruggling movements often led to more piercings of the bug on the sameor additional legs. Additional piercings can occur because the trichomesare of sufficient density that all legs are surrounded by trichomes(FIG. 1B) (average 99 trichomes/mm², sd=53, n=11 leaves; this trichomedensity is comparable to that reported in the literature for P.vulgaris). (See, Pillemer E & Tingey W., Science 193, 482-484 (1976),the disclosure of which is incorporated herein by reference.)Examination of all legs of a set of captured bugs in LV-SEM showed anaverage of 3.8 piercings/bug (range 1-7 piercings/bug, n=6 bugs, 36legs). The most common location for piercing was underneath thepretarsal claws (FIG. 5A, c; 61% of the 23 piercings on the six bugs).The other common location on the legs where piercing occurred was in theintersegmental membrane between the 1st and 2nd tarsal subsegments (FIG.5B; 30% of the 23 piercings on the six bugs; tarsal subsegments werecounted from proximal to distal).

To monitor whether captured bugs were able to free themselves from aleaf, photographs were taken of bug positions on leaves at ten-minuteintervals for thirty minutes following capture. The average displacementof a bug thirty minutes after capture on a bean leaf was only 3.2 mm(range 1.4-9.9 mm; n=6 bugs), consistent with rotation in place around apierced leg (˜6 mm, see above). Captured bugs struggled, but were onlyrarely able to generate enough force to pull free of a piercing trichome(by breaking the trichome or ripping the insect cuticle), and usuallyimmediately got recaptured on the leaf. If a bug was able to break atrichome, there should be evidence on the undersurface of the leg. Tomeasure this some bugs were forcibly detached from leaves by pullingstraight up with forceps, and immediately examined them upside-down inLV-SEM to look for attached broken trichomes or physical damage to theunderside (ventral surface) of the bug legs, which would provide suchevidence. In 8 out of 9 cases, it was possible to identify at least onebroken trichome still attached to the bug (FIG. 6), and in the remainingcase, there was evidence of damage (leaking hemolymph in the piercedlocation). Therefore it was possible to confirm earlier piercings fromdamage on the undersides of bug tarsi. Bugs that had been momentarilysnagged, but not captured by leaves, never exhibited any evidence ofpiercing when examined using LV-SEM; presumably their legs had only beenhooked.

EXAMPLE 2 Microfabrication and Characterization of Biomimetic Surfaces

The bean leaves captured bed bugs so quickly and effectively that alogical starting place for microfabrication of a capturing surface forbed bug control is to faithfully reproduce the leaf trichomes with therelevant surface density and orientation. The hardest challenges in themicrofabrication of the high aspect ratio trichomes on a replicate beanleaf surface are to accurately reproduce the sharp tips and the recurvedshapes.

Synthetic surfaces were generated with indistinguishable trichomegeometry and hook point sharpness seen in natural leaves (FIGS. 3A to3E). The kidney bean trichomes had an average tip sharpness of 220±35 nm(mean±1 standard deviation, n=16 trichomes from 16 different leaves) andthe synthetic replicas had an average tip sharpness of 230±50 nm (mean±1standard deviation, n=27 from 27 different synthetic surfaces); tipsharpness is not significantly different in a one-way ANOVA (P=0.49).Therefore the method is accurately duplicating the geometry of themicrostructures on the natural surfaces.

Serendipitously it was discovered that natural trichome tips wouldsometimes be retained in the negative mold material (FIG. 4) and becomeincorporated into hybrid surfaces (FIG. 7). This allowed us to generatesurfaces that had trichomes with natural piercing hook tips attached tosynthetic stalks (hybrid trichomes). The natural tips were usuallyindistinguishable in appearance from synthetic tips when viewed in SEM(FIG. 7B). Therefore to reliably identify natural trichome tips, energydispersive X-ray spectroscopy (EDS) was used to look for silicon, whichwas present in large amounts in the natural trichome tips (FIGS. 7B &7C), but not in the synthetic polymers used (FIG. 7b ). EDS mapping wasused to estimate the percentage of natural tips on the microfabricatedsurfaces (FIG. 7D). The percentage of natural tips ranged from 0-100% inthe 38 microfabricated surfaces that were characterized by EDS mapping.

If the hybrid trichomes (with natural tips) are able to hook or piercethe bed bugs, but the completely synthetic trichomes are not, syntheticsurfaces with a larger percentage of hybrid trichomes should interferemore with bed bug locomotion than synthetic surfaces with fewer hybridtrichomes. Therefore the number of locomotory cycles expected togenerate a snag or capture could be predicted by correcting aconservative standard (19 locomotory cycles, the 90th percentile forcapture on natural leaves) for the percentage of hybrid trichomesestimated using EDS. Only 4 out of 26 bugs showed a momentary snagwithout capture during the number of locomotory cycles that would beexpected to result in capture 90% of the time for their particularsurface.

If the bugs were not captured by synthetic surfaces because they wereable to break the synthetic or hybrid trichomes, broken trichomes shouldbe evident on the microfabricated surfaces after bugs ran on them. Inorder to evaluate whether trichomes on microfabricated surfaces aresnapped off by the bugs, SEM images of three surfaces were compared bothbefore and after ten bugs were confined on each surface for 18 hours(the surfaces were rotated constantly to keep the bugs moving). Not asingle broken trichome was observed out of the several hundred trichomesviewed, suggesting that neither synthetic nor hybrid trichomes arebreaking when the bugs are walking on them.

In order to further validate the fidelity of the proposed replicationprocess, different bean leafs were reproduced and both the negative andthe positive molds were examined using standard high vacuum scanningelectron microscopy (SEM) techniques. The negative mold wasfreeze-fractured, mounted to view the cross section, and then sputtercoated with gold. The resulting SEM is shown in FIGS. 8A to 8C, whichclearly shows trichome microstructures whose geometry has remainedintact. Likewise, FIGS. 9A to 9C shows representative images of thepositive leaf replicas. A low magnification image of epoxy hooksreplicating Phaseolus coccineus (Scarlet Runner bean) is shown in FIG.9B. (In this image the larger veins are visible along with the trichomeson the surface.) FIG. 9C is a closer view of a biomimetic vein withsharp replicated hooks created from a Phaseolus vulgaris (kidney bean)leaf. The higher magnification image shows one of the epoxy sharp hooksreplicating Phaseolus coccineus (Scarlet Runner bean). Various epoxiesand glues with different hardening rates and resin:hardener ratios weretried. In this embodiment, the kidney bean leaf replica is made fromTiteBond III, a type of wood glue. These images clearly demonstrate thatthe double molding process described in FIG. 3 can indeed generatebiomimetic surfaces containing hooked trichomes with precision.

Conclusion

In this disclosure, the mechanism of bed bug capture by themicrostructures of plant leaf surfaces, including three species of beanplants, were characterized and then employed in the design andfabrication of biomimetic insect capture surfaces for insect capture.Specifically, four different plant species have been examined,including: Phaseolus vulgaris, Phaseolus coccineus, Phaseolus limensis,and Passiflora morifolia. All four plant species have similar surfacetexture consisting of hooked trichomes, which can impale or hook bed bugtarsi. The interaction between the plant microstructure and bed bugtarsi has been documented by both videography and low vacuum scanningelectron microscopy (LV-SEM). Furthermore, the location of trichomepiercing on bed bug legs has been determined.

One way to duplicate the mechanical properties of the natural surface isto match both the geometry and the material properties of the syntheticsurface to the natural leaf. Using leaf surfaces as models, biomimeticpolymeric surfaces for the capture of insects, including bed bugs havebeen formed and tested. In addition, a process for constructing theseinsect capture surfaces. In some embodiments, the process istwo-fold: 1) a negative mold of the leaf is made, and 2) a secondmaterial is then poured onto the negative mold, which generates apositive leaf replica. This method is further shown to faithfullyreproduce the functional aspects of the plant trichomes. The moldingprocess generated microfabricated trichomes that were indistinguishablefrom the natural trichomes, with the proper aspect ratio and sharpnessof tips, arranged with the same density, orientation and height seen onthe natural leaves.

Capturing bed bugs (or other insects) with microfabricated surfaces is aphysical rather than a chemical approach, and therefore leaves nochemical residue, and does not expose people to pesticide treatments.This is a sustainable “green technology.” By incorporatinginsect-trapping microfabrications into substrates (carpet, rugs,drapery, dust ruffles, suitcases, etc.) the invention also would enablemonitoring and prevention of future infestations in homes, hotels,dormitories, schools, offices, and other dwellings. This device can thenbe used in bed bug abatement to capture bed bugs for detection orcontrol. For detection, the insect-entrapping microfabrications could beincorporated into panels, strips, ropes, etc., and placed in strategicareas to alert building occupants, property managers, etc. of thepresence of infestation. As a control device it could also beincorporated into the manufacture of carpet, rugs, drapes, dust ruffles,bedding, upholstery, and other furnishings for both prevention andremediation of infestations. No such device currently exists for bed bugabatement. A device that captures bed bugs by surface microfabricationhas great potential in commercial applications as bed bugs are anescalating international problem in all manner of buildings, andtherefore it is expected that this device will have widespread use.

Doctrine Of Equivalents

Those skilled in the art will appreciate that the foregoing examples anddescriptions of various preferred embodiments of the present inventionare merely illustrative of the invention as a whole, and that variationsin the steps and various components of the present invention may be madewithin the spirit and scope of the invention. Accordingly, the presentinvention is not limited to the specific embodiments described hereinbut, rather, is defined by the scope of the appended claims.

What is claimed is:
 1. A microfabricated insect capturing surfacecomprising: a substrate defining a plane; a plurality of insect capturesurface microstructures each formed from a flexible elongated member,the plurality of surface microstructures being disposed on the substratewith a variable orientation to the plane of the substrate and at adensity sufficient such that multiple insect capture surfacemicrostructures are capable of simultaneously interacting with an insectdisposed thereon; wherein at least some of the surface microstructureshave a recurved body capable of entangling the insect, and wherein atleast some of the surface microstructures include a piercing elementbeing sufficiently rigid and sharp to pierce the insect body; andwherein the surface microstructures are formed from a material having abreaking stress sufficiently large to avoid breakage during interactionwith the insect.
 2. The microfabricated surface of claim 1, wherein eachof the plurality of insect capture surface microstructures has arecurved body and wherein at least one piercing element is incorporatedonto each of said insect capture surface microstructures.
 3. Themicrofabricated surface of claim 2, wherein the piercing element isdisposed at the terminating end of the elongated member.
 4. Themicrofabricated surface of claim 2, wherein the surface microstructuresinclude at least two piercing elements, and wherein the piercingelements are disposed along the body of elongated member.
 5. Themicrofabricated surface of claim 1, wherein the recurved body is formedin a shape selected from the group consisting of a hook, curve, loop orhoop.
 6. The microfabricated surface of claim 1, wherein the piercingelement is selected from the group consisting of a sharp point, hook orbarb.
 7. The microfabricated surface of claim 1, wherein the pluralityof surface microstructures are dimensioned such that engage theunderside of the insect.
 8. The microfabricated surface of claim 1,wherein the piercing element has a diameter of about 100 to 1000 nm. 9.The microfabricated surface of claim 1, wherein the elongated member hasa Young's Modulus of from 1 to 23 GPa.
 10. The microfabricated surfaceof claim 1, wherein the surface microstructures are modeled on a planttrichome.
 11. The microfabricated surface of claim 10, wherein the planttrichome is modeled on one plant selected from the group Phaseoluscoccineus, Phaseolus vulgaris, Phaseolus limensis, Passiflora morifolia,Cynnoglossum offtcinale and Caiophora coronaria.
 12. The microfabricatedsurface of claim 1, wherein the surface microstructures are disposed onthe substrate in a density of between 20 to 300 surface microstructuresper square millimeter.
 13. The microfabricated surface of claim 1,wherein the surface microstructures are formed from a material selectedfrom the group consisting of polymeric materials, natural fibers,metals, oxides and nano- or micro-engineered structures.
 14. Themicrofabricated surface of claim 1, wherein the elongated member isformed of a hollow body.
 15. A method of manufacturing a microfabricatedinsect capturing surface comprising: providing a substrate defining aplane; disposing a plurality of insect capture surface microstructuresthereon, each formed from a flexible elongated member, the plurality ofsurface microstructures being disposed on the substrate with a variableorientation to the plane of the substrate and at a density sufficientsuch that multiple insect capture surface microstructures are capable ofsimultaneously interacting with an insect disposed thereon; wherein atleast some of the surface microstructures have a recurved body capableof entangling the insect, and wherein at least some of the surfacemicrostructures include a piercing element being sufficiently rigid andsharp to pierce the insect body; and wherein the surface microstructuresare formed from a material having a breaking stress sufficiently largeto avoid breakage during interaction with the insect.
 16. The method ofclaim 15, wherein each of the plurality of insect capture surfacemicrostructures has a recurved body and wherein at least one piercingelement is incorporated onto each of said insect capture surfacemicrostructures.
 17. The method of claim 16, wherein the piercingelement is disposed at the terminating end of the elongated member. 18.The method of claim 16, wherein the surface microstructures include atleast two piercing elements, and wherein the piercing elements aredisposed along the body of elongated member.
 19. The method of claim 15,wherein the recurved body is formed in a shape selected from the groupconsisting of a hook, curve, loop or hoop.
 20. The method of claim 15,wherein the piercing element is selected from the group consisting of asharp point, hook or barb.